Thank you very much for your mail.
First of all , let me give you more information aboout my system. This is not intel 32 , this is
itanium 64 . By using getpagesize() i have found that page size is 16kb.
I have 8gb. ram , 4 cpus , and oracle 18.104.22.168 rac ( parallel server - so i have 2 servers )
I use emc disk array , raid 10 , 2TB. data , and 1 hba (fibre channel)
The file system which data files reside is OCFS ( oracle clustered file system) which i told by oracle that uses direct io .
You are right that all memory is virtual both in linux and solaris.
When i strace the oracle executables i see it uses pread calls for io . My concern is , if oracle executable does not use direct io then the kernel uses virtual memory system in order to cache the data ( i mean inside the page cache - not buffer cache which only caches inode information both on solaris and linux) , at the same time the data is cached inside the oracle executables private area so , doesnt this mean double buffering and wasting of memory?